Image sensor manufacturing method

Abstract

A method of manufacturing an image sensor comprising the forming of an opening in a substrate, the forming of a conductive pad covering the flanks of the opening and delimiting a gap in the opening, the forming of microlenses in a layer made of a first resin, the layer made of the first resin covering the pad and penetrating into the gap, the forming of a mask made of a second resin on top of and in contact with the layer made of the first resin, the chemical plasma etching of the layer made of the first resin, through the mask, delimiting a block of the first resin in the gap, the deposition of a protective layer on the microlenses and on the block, the removal of the portion of the protective layer covering the block, and the etching of the block.

1 . A method of manufacturing an image sensor, the method comprising the following steps, in order:
 a) forming of an opening in a semiconductor substrate comprising a first surface and a second surface opposite to the first surface, the opening extending from the first surface to the second surface, and the forming of at least one electrically-conductive pad comprising a first portion extending over the first surface and a second portion covering flanks of the opening and delimiting a gap in the opening;   b) forming a plurality of microlenses in a layer made of a first resin, the layer made of the first resin covering the electrically-conductive pad and penetrating into the gap;   c) forming a mask made of a second resin on top of and in contact with the layer made of the first resin;   d) chemical plasma etching of the layer made of the first resin, through the mask delimiting a block of the first resin in the gap;   e) depositing a protective layer on the plurality of microlenses and on the block;   f) removing a portion of the protective layer covering the block; and   g) chemical plasma etching the block.   
     
     
         2 . The method according to  claim 1 , further comprising, at step a), forming a plurality of photodetectors in the semiconductor substrate. 
     
     
         3 . The method according to  claim 1 , wherein during step d), the electrically-conductive pad is exposed. 
     
     
         4 . The method according to  claim 1 , wherein, at step b), the forming of the plurality of microlenses includes a step h) of forming structures in a form of microlenses in a layer made of a third resin, followed by a step i) of transferring the structures into the layer made of the first resin by physical etching. 
     
     
         5 . The method according to  claim 4 , wherein, at step h), the structures are formed by photolithography and flow. 
     
     
         6 . The method according to  claim 1 , wherein, after step d), the mask is removed using a solvent. 
     
     
         7 . The method according to  claim 1 , wherein the layer made of the first resin is crosslinked. 
     
     
         8 . The method according to  claim 1 , wherein the layer made of the first resin is non-photosensitive. 
     
     
         9 . The method according to  claim 1 , wherein the plasma used at steps d) and g) comprises oxygen. 
     
     
         10 . The method according to  claim 1 , wherein the protective layer is made of an oxide. 
     
     
         11 . The method according to  claim 10 , wherein the protective layer is made of silicon oxynitride (SiON). 
     
     
         12 . An image sensor, comprising:
 a semiconductor substrate, including:
 a plurality of photodetectors in the semiconductor substrate; 
 a first surface and a second surface opposite to the first surface; and 
 a first opening extending from the first surface to the second surface; 
   an electrically-conductive pad comprising a first portion extending over the first surface and a second portion covering flanks of the first opening and delimiting a gap in the first opening;   a layer made of a first resin covering the first surface in which a plurality of microlenses are formed, the layer made of the first resin comprising a second opening facing the electrically-conductive pad, the second opening having inclined side walls; and   a protective layer covering the layer made of the first resin, the protective layer does not extend inside or on top of the gap.   
     
     
         13 . The image sensor of  claim 12 , wherein the inclined side walls extend to the first surface of the semiconductor substrate. 
     
     
         14 . The image sensor of  claim 12 , further comprising a first insulating layer on the first surface of the substrate, the first insulating layer being between the electrically-conductive pad and the substrate. 
     
     
         15 . The image sensor of  claim 14 , further comprising a second insulating layer on regions of the electrically-conductive pad. 
     
     
         16 . The image sensor of  claim 15 , wherein the second insulating layer is in the gap. 
     
     
         17 . A method, comprising:
 forming a conductive pad in a first through opening in a substrate, the substrate having a first surface opposite a second surface, the first through opening extending from the first surface to the second surface, the conductive pad being on the first surface and extending between sidewalls of the substrate, the conductive pad having sidewalls facing each other and delimiting a gap;   forming a first resin layer on the first surface of the substrate and forming a plurality of microlenses, a portion of the first resin layer being in the gap, the first resin layer being on the conductive pad, the plurality of microlenses being made of the first resin; and   removing the portion of the first resin layer in the gap and exposing a region of the conductive pad.   
     
     
         18 . The method of  claim 17 , wherein removing the portion of the first resin layer forms slanted sidewalls of the first resin layer, the slanted sidewalls extending to the first surface of the substrate. 
     
     
         19 . The method of  claim 17 , wherein removing the portion of the first resin layer includes:
 forming a protective layer on the plurality of microlenses, the conductive pad, and over the gap, including the portion of the first resin layer in the gap;   forming a second resin layer on the protective layer; and   removing a portion of the second resin layer, the removed portion of the second resin layer being over the gap.   
     
     
         20 . The method of  claim 17 , wherein removing is carried out via chemical plasma etching.